1. Field of the Invention
The present invention relates to an private exchange and a call signal exchanging method thereof, in particular to an internet phone-based private exchange and a call signal exchanging method thereof which is capable of communicating between terminals supporting different protocols in a local area network, and communicating any terminal connected with the local area network and a terminal connected with PSTN.
2. Description of the Prior Art
In general, an office according to prior art has two networks which are connected with Private Branch Exchange (PBX) system to support telephone communication and a network facility to support data communication. Accordingly, the office has problems occurred by the conventional networks as below.
First, both telephone line connected to a private exchange for audio communication and LAN (Local Area Network) cable connected to LAN for data communication are separately led-in and installed, and the two communication lines are allotted to one user, accordingly lots of installation cost and plenty of time for wiring work are required.
In addition, later installing additionally more private exchanges is difficult because private exchanges adopt different exchange methods according to its manufacturer, when the office is moved to other place, changing information of the private exchange is difficult because the private exchange has to be set by manual operation in accordance with installation place.
Accordingly, double management costs are required because the each communication apparatus has to be kept separately in order to perform voice communication and audio communication.
Second, there are lots of limitations to determine switching capacity and switching speed of the conventional private exchange adopting a circuit switching method which converts audio signals into time slots, allots it to communication channel, and transmits the time slots through a memory buffer, and there are lots of limitations to determine switching speed of the conventional private exchange which adopts a HDLC method aside from audio communication.
In addition, the conventional private exchange has complicated structure and control software because audio signal channel and data signal channel are duplicated, and it is mainly for audio communication, accordingly interlocking with other data communication apparatus performing multimedia through internet is difficult.
Third, on the basis of the conventional technology, in order to reduce telephone bill, a company hires telephone leased-line for telephone call and international call between a headquarter and branches by paying a certain amount of money every month.
In addition, in order to connect to internet, WAN (Wide Area Network) is constructed between the headquarter and the branches, the headquarter is connected to an ISP (Internet Service Provider) which provides internet leased-lines, and the branches are connected to internet by paying a certain amount of money every month.
Accordingly, the company has to install and maintain leased-lines doubly, and has to pay the bill doubly.
However, traffic on the telephone leased-line is very light except a certain busy time zone, and there is a way to perform audio communication not using the telephone leased-line but routing audio communication through WAN for connecting internet, accordingly the company can reduce the communication bill.
In the latest communication technologies, a private exchange adopting the conventional circuit switching method is replaced with an IP based private exchange, accordingly calling telephone through Internet is possible.
The IP based private exchange can communicate on the basis of H.323 standard call control presented by ITU-T as an international standard, and makes terminals corresponding to H.323 protocol communicate.
The H.323 protocol is a communication protocol which makes terminals having CODEC for processing audio signals and video signals communicate each other through internet, it requires 15xcx9c20 seconds for call connection and makes terminals placed at two points (point to point) communicate.
Accordingly, the IP based private exchange managing traffic on LAN or internet requires a property protocol which spends short time for call connection, holds status information of PSTN and terminals in common inside of a group, and reduces traffic by multicasting the status information to other terminals.
Meanwhile, because the conventional private exchange and the IP based private exchange control calls by a central studio system, when all call requests are transmitted to the IP based private exchange, the private exchange connects or ends the calls in accordance with the status of the terminal, and the IP based private exchange makes only IP terminals reach each other internally or makes PSTN call reach when the IP based private exchange is connected to the private exchange.
When the terminals and the private exchange are made so as to have a distributed call control method processing each call by itself, the terminals and the private exchanges can be easily installed, and failures to be occurred are distributed, accordingly the terminals and the private exchanges can be installed and maintained stably.
In the distributed call control method, a certain terminal or private exchange informs its information to the other terminal or the other private exchange within broadcasting extent by transmitting its ID through IP network.
After, all status information related to calls is changed on the terminal or the private exchange, and the changed status information is multicast as a message pattern.
The other terminal or the other private exchange receiving the multicast message renews status information of the terminal and the private exchange stored before, and at the same time displays the received status information on a display unit such as a LED or a LCD.
However, speech quality of the terminal adopting the distributed call control method lowers during telephone-talk because the terminal has to receive status information from a plurality of terminals or private exchange while it is busy.
It is an object of the present invention to provide an internet phone-based private exchange and a call signal exchanging method thereof which is capable of supporting local area network communication between terminals when terminals having different protocol are connected each other, and supporting external communication between the terminals and terminals connected to external PSTN.
To achieve above object, an internet phone-based private exchange comprises a network protocol unit which inputs call signals transmitted from call transmitting terminals connected to local area network and processes the call signals at a real time, a call signal detecting/determining unit which detects the call signals outputted from the network protocol unit and determines protocol types of the call signals of the call transmitting terminals, terminal gate keepers which make possible communication between terminals supporting protocol of the call transmitting terminals through the network protocol unit, a call converting unit which is connected to the terminal gate keepers and matches a protocol of the call signal generated from the call transmitting terminal with a protocol of a call signal supporting a receiving terminal which is to be connected by the call transmitting terminal when the protocol of the call signal of the call transmitting terminal and that of the receiving terminal are different, and a task managing unit which inputs the call signals of the call transmitting terminals from the gate keepers and transmits IP addresses of the receiving terminals which are to be connected by the call transmitting terminals to the terminal gate keepers.
In order to achieve above object, a call signal exchanging method of a private exchange based on internet phone comprises the steps of detecting a call signal transmitted from a call transmitting terminal and determining protocol of the call, matching the protocol of the call protocol with protocol of a call supported by a call receiving terminal when the protocol supported by the call transmitting terminal and the protocol supported by the receiving terminal are different, and transmitting the call signal from the call transmitting terminal to the receiving terminal.
In order to achieve above object, a call signal exchanging method of a private exchange based on internet phone comprises the steps of judging whether a call signal generated by a first call transmitting terminal is to be connected to local area network or to be connected to PSTN, and transmitting the call signal to the PSTN when the call signal is for being connected to the PSTN.
In order to achieve above object, a call signal exchanging method of a private exchange based on internet phone comprises the steps of searching whether a first receiving terminal corresponding to a call signal is registered on a memory after being inputted the call signal received from a PSTN, and transmitting the call signal to the first receiving terminal when the first receiving terminal is registered on the memory.